In the automobile industry, radiation-assisted connecting methods are extensively used for body construction, such as, for example, electron beam, laser beam and laser hybrid welding methods. The number of welding connections, in particular including the welding seams, has significantly increased in past decades. Accordingly, there is a great need in the automobile industry for systems allowing automatic inspection and control of welding seams.
The most varied types of defects may occur in the production of welding seams. Defects of this type are, for example, a length which is too short, insufficient full penetration welding, a crack, a cut, a hole, a pore or a blow hole. A reliable inspection of welding seams assumes that defects of the most varied types can be reliably detected and recognised.
A method for checking a welding seam is known from DE 100 04 049 A1, in which the heat radiation in the region of the welding seam is detected as an image with the aid of a digital infrared camera and compared with a previously recorded reference image using a computer. The quality of the welding seam is assessed using the comparison. However, this method does not ensure a reliable inspection of the welding seam, in particular if defects of various types occur.
Furthermore, a method for automatic destruction-free checking of a welding seam is known from DE 103 26 377 B3, in which the welding seam is heated and a thermography sensor is moved on a checking path, which detects the temperature values at each point of the checking path. The temperature values may be evaluated as quality features of the welding seam and shown in a position-related manner with respect to the welding seam. This method does not ensure reliable inspection of the welding seam either, in particular if defects of various types occur.